1. Field of the Invention
The present invention relates to an apparatus for separation/enrichment of isotopes of a uniform compound, and to an apparatus and method for obtaining heavy oxygen water in which the oxygen isotopes 17O and 18O (referred to as heavy oxygen isotopes) within the water molecules have been enriched. More specifically, the present invention relates to a method of producing water enriched in the oxygen isotopes of 17O and 18O in which oxygen is enriched in 16O17O, 16O18O, 17O17O, 17O18O, and 18O18O by cryogenic distillation of oxygen, and then converted to water, and to a method of producing water which is further enriched in the oxygen isotopes of 17O and 18O in which oxygen is enriched in 16O17O, 16O18O, 17O17O, 17O18O, and 18O18O by cryogenic distillation of oxygen, and then converted to water which is then subject to water distillation.
2. Description of the Related Art
In the distillation operation in a system in which the relative vapor pressure (separation factor) is extremely small, as represented by the process of distillation separation/enrichment of isotopes, an extremely large theoretical number of plates is necessary.
In this case, generally, packed columns are used in order to suppress pressure loss within the column. However, it is not uncommon for the required packing height therefor to reach several hundred meters.
Consequently, actual apparatuses are constructed with a plurality of distillation columns connected by piping, the whole of which comprises a single distillation column group.
FIG. 18 shows an example of an apparatus provided with three distillation columns with each of the columns (first to third columns 61, 62, and 63) connected.
In this apparatus, the liquid which accumulates in the bottom of the first distillation column 61 and the second distillation column 62 is supplied by means of pumps 61a and 62a to the tops of second distillation column 62 and third distillation column 63 respectively as reflux liquid. Vapor which is drawn off from the top of the second column 62 and the third column 63 is returned to the bottoms of the first column 61 and the second column 62 respectively as ascending vapor.
In this process, the supply of the process fluid from the first column 61 to the second column 62 and from the second column 62 to the third column 63 is carried out by liquid pumps 61a and 62a, but the return of the process liquid from the second column 62 to the first column 61, and from the third column 63 to the second column 62 occurs due to the pressure differences in the vapor. Therefore, the pressure within the distillation columns must be successively higher from the first column 61 toward the third column 63. In general, since the relative vapor pressure (separation factor) is smaller the higher the operating pressure of the distillation column, distillation efficiency is lower in the second column 62 than the first column 61, and lower in the third column 63 than in the second column 62.
In addition, in general, as in isotope separation processes, when the relative vapor pressure of the separation components is extremely small and the packing height is extremely large, the time (hereinafter referred to as the start-up time) from the start up of the apparatus until it becomes possible to collect the stipulated amount (the product amount extracted in accordance with the specifications, or the planned value) may take from several months to several years. Consequently, reduction of the start-up time has hitherto been an issue.
The start-up time is heavily dependent on the process liquid hold-up within the apparatus, and the greater the amount thereof, the longer the start-up time is.
FIG. 19 shows a distillation process having the same functions as the apparatus shown in FIG. 18, and each column 71, 72, and 73 is provided with condensers 5, 7 and 9, and reboiler 6, 8, and 10. These are apparatuses which are generally used in processes comprising a plurality of distillation columns. The diameter of the distillation columns becomes smaller from the column 71, to which the starting material is fed, to the column 73, which is downstream from column 71.
However, even when using this type of apparatus, since the pressure within the distillation column increases from the first column 71 to the third column 73, in the same way as with the apparatus shown in FIG. 18, the distillation efficiency is lower in the second column 72 than in the first column 71, and is lower in the third column 73 than in the second column 72.
Thereby, it is possible to reduce the process liquid hold-up within the apparatus, and to shorten the start-up time.
Reductions in the distillation efficiency lead to increases in the necessary packing height of the distillation column and to increases in the process liquid hold up. Therefore, they are not desirable from the point of view of shortening the start-up time.
In addition, in conventional isotope distillation processes, columns packed using unstructured packing have been used. In general, unstructured packing has a larger specific surface area compared with structured packing. However, the liquid hold-up within the distillation column is 10 to 20% of the volume of the column, and in some cases exceeds 20%, and this is a cause of prolonged start-up time.
In consideration of the above-mentioned circumstances, the present invention has, as an object the provision of an apparatus comprising a plurality of distillation columns and with which the start-up time is shorter than with conventional apparatuses.
In order to overcome the above-mentioned problems, the apparatus of the present invention is an apparatus for separation of a vapor or liquid mixture comprising a plurality of distillation columns (a first column to an nth column) constructed in a cascade comprising introduction conduits which connect the bottom of a kth column (1xe2x89xa6kxe2x89xa6(nxe2x88x921)) or an outlet of a reboiler provided in the vicinity of the bottom of the kth column to the t op of a (k+1)th column, an inlet of a condenser provided in the vicinity of the top of the (k+1)th column, or the middle section of the (k+1)th column, and return conduits which connect an outlet of the condenser of the (k+1)th column to an inlet of the reboiler provided in the vicinity of the bottom of the kth column, the bottom of the kth column, or the middle section of the kth column.
In addition, the apparatus of the present invention is an apparatus for separation on a vapor or liquid mixture comprising a plurality of components using a plurality of distillation columns (a first column to an nth column) constructed in a cascade comprising introduction conduits which connect the bottom of a kth column (1xe2x89xa6kxe2x89xa6(nxe2x88x921)) or an outlet of a reboiler provided in the vicinity of the bottom of the kth column to the top of a (k+1)th column, an inlet of a condenser provided in the vicinity of the top of the (k+1)th column, or the middle section of the (k+1)th column, and return conduits which connect the top of the (k+1)th column, or the inlet of the condenser provided in the vicinity of the top of the (k+1)th column to the bottom of the kth column or the middle section of the kth column via a blower.
In addition in the apparatus of the present invention, at least one of the distillation columns is a packed column in which structured packing (promoting-fluid-dispersion type structured packing or non-promoting-fluid-dispersion type structured packing) is used, or a wetted wall column.
In addition, the apparatus of the present invention comprises an isotope scrambler, an extraction conduit which connects at least one section of said apparatus to an inlet of the isotope scrambler; and a return conduit which connects at least one section of said apparatus to an outlet of the isotope scrambler.
In addition, the apparatus of the present invention comprises a hydrogenation device at a stage after the nth column.
In addition, the apparatus of the present invention is provided with a hydrogenation device at a stage after the nth column, and another of the above-mentioned plurality of distillation columns (a first column to an nth column) constructed in a cascade, at the above-mentioned stage.
The method of enrichment of oxygen isotopes of the present invention is one in which an oxygen-starting material containing heavy oxygen isotopes is enriched by means of a cascade process using a plurality of distillation columns (a first column to an nth column) comprising supplying at least a part of the vapor from the bottom of a kth (1xe2x89xa6kxe2x89xa6(nxe2x88x921)) column or an outlet of a reboiler provided in the vicinity of the bottom of the kth column to the top of a (k+1)th column, an inlet of a condenser provided in the vicinity of the top of the (k+1)th column, or a middle section of the (k+1)th column; returning at least a part of the liquid from the top of the (k+1)th column or an outlet of the condenser of the (k+1)th column to an inlet of a reboiler of the kth column, the bottom of the kth column, or the middle section of the kth column; and thereby carrying out enrichment in at least one type of oxygen molecule of 16O17O, 16O18O, 17O17O, 17O18O, and 18O18O, which contain heavy oxygen isotopes.
A method of enrichment of oxygen isotopes in which an oxygen-starting material containing heavy oxygen isotopes is enriched by means of a cascade process using a plurality of distillation columns (a first column to an nth column) comprising supplying at least a part of the vapor from the bottom of a kth(1xe2x89xa6kxe2x89xa6(nxe2x88x921)) column or an outlet of a reboiler provided in the vicinity of the bottom of the kth column to the top of a (k+1)th column, an inlet of a condenser provided in the vicinity of the top of the (k+1)th column, or a middle section of the (k+1)th column, pressurizing at least a part of a vapor drawn off from the top of a (k+1)th column or a vapor from an inlet of the condenser of the (k+1)th column by means of a blower, and then returning a said vapor to the bottom of the kth column or the middle section of the kth column, and thereby carrying out enrichment in at least one type of oxygen molecule of 16O17O, 16O18O, 17O17O, 17O18O, and 18O18O, which contain heavy oxygen isotopes.
In addition, the method of the present invention is a method for enrichment in isotopes of oxygen comprising subjecting an oxygen isotope-enriched material enriched by means of the above mentioned enrichment method to oxygen isotope scrambling to obtain an enriched product having an even higher concentration of at least one type of the above mentioned oxygen molecules which contain heavy oxygen isotopes.
In addition, the method of the present invention is a method for enrichment in isotopes of oxygen comprising subjecting an oxygen isotope-enriched material enriched by means of the above mentioned method of enrichment to oxygen isotope scrambling, to obtain an enriched material having a higher concentration of at least one type of said oxygen molecules which contain heavy oxygen isotopes; and obtaining an enriched product having an even higher concentration of at least one type of the above mentioned oxygen molecules which contain heavy oxygen isotopes by means of conducting the above mentioned method of enrichment again on said enriched material.
In addition, the method of producing heavy oxygen water of the present invention comprises obtaining an enriched material which has been enriched in at least one component from oxygen molecules which contain heavy oxygen isotopes by means of cryogenic distillation of an oxygen-staining material which contains heavy oxygen isotopes using the above mentioned apparatus; obtaining water containing heavy oxygen water corresponding to said enriched material by adding hydrogen to said enriched material. Thereafter, this heavy oxygen water is further enriched using the above mentioned apparatus.
In addition, the method of the present invention is a method of producing heavy oxygen water in which a water-starting material containing heavy oxygen water is enriched by means of a cascade process using a plurality of distillation columns comprising supplying at least a part of the water vapor from the bottom of a kth (1xe2x89xa6kxe2x89xa6(nxe2x88x921)) column, or an outlet of a reboiler provided in the vicinity of the bottom of the kth column to the top of a (k+1)th column, an inlet of a condenser provided in the vicinity of the top of the (k+1)th column, or a middle section of the (k+1)th column, introducing at least a part of the water from the top of the (k+1)th column, or an outlet of the condenser of the (k+1)th column into an inlet of a reboiler of the kth column, the bottom of the kth column, or the middle section of the kth column, and thereby carrying out enrichment in at least one type of heavy oxygen water of H217O, H218O, D217O, D218O, DH17O, DH18O, which contain heavy oxygen isotopes.
In the present invention, [since an introduction conduit which connects the bottom of the kth column (1xe2x89xa6k xe2x89xa6(nxe2x88x921)) or an outlet of a reboiler provided in the vicinity of the kth column to the top of the (k+1)th column, or the middle section of the (k+1)th column, and a return conduit which connects the outlet of the condenser of the (k+1)th column to the inlet of a reboiler provided in the vicinity of the bottom of the kth column, the bottom of the kth column, or the middle section of the kth column are provided,] it is possible to return a part of the liquid drawn off from the condenser of the (k+1)th column via a return conduit. More particularly, an introduction conduit may connect the bottom of the kth column (1xe2x89xa6k xe2x89xa6(nxe2x88x921)) or an outlet of a reboiler provided in the vicinity of the kth column to the top of the (k+1)th column. Alternatively, the introduction conduit may connect to the middle section of the (k+1)th column. Similarly, a return conduit may connect the outlet of the condenser of the (k+1)th column to the inlet of a reboiler provided in the vicinity of the bottom of the kth column, the bottom of the kth column, or the middle section of the kth column.
For this reason, it is possible to set the pressure in each column lower than in conventional apparatuses, to increase the relative vapor pressure between each of the isotopes within each column, and thereby it is possible to improve distillation efficiency.
Consequently, it is possible to reduce the height of the packing within each column, and it is possible to shorten the start-up time. In addition, it is possible to obtain a product having a higher concentration of heavy oxygen isotopes.
In addition, the liquid hold-up volume is reduced, and this make it possible for the start-up time of the device to be reduced even further.